There are a couple of sealed bass omnis, the Avantage audio César from France, though maybe not available that widely, has a 10” sealer bass driver firing down at a deflector cone and a pair of smaller, opposed, wide range drivers run unfiltered firing at back to back cones further up, all in sealed enclosures, though said enclosures don’t seem particularly inert to the touch. I’ve heard a pair and there was a lot to like.
The other is German Physiks with their Ohme Walsh, if that’s how it’s spelt, derived cones mated with sealed bass units, except for the unicorn which is a horn rear loaded single driver.
I think the Fern and Roby Raven two full ranger is sealed.
Manger from Germany make some sealed floor standers.
Magico.
Audionote UK K series but they’re not that big.